Titanium aluminum and tantalum aluminum thin films

ABSTRACT

A process for depositing titanium aluminum or tantalum aluminum thin films comprising nitrogen on a substrate in a reaction space can include at least one deposition cycle. The deposition cycle can include alternately and sequentially contacting the substrate with a vapor phase Ti or Ta precursor and a vapor phase Al precursor. At least one of the vapor phase Ti or Ta precursor and the vapor phase Al precursor may contact the substrate in the presence of a vapor phase nitrogen precursor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/919,180, filed Oct. 21, 2015, which claims the benefit of U.S.Provisional Application No. 62/067,802, filed Oct. 23, 2014, each ofwhich is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates generally to vapor deposition processes,and more particularly, to deposition of titanium aluminum or tantalumaluminum thin films.

Description of the Related Art

Titanium aluminum or tantalum aluminum containing thin films may be usedin a variety of contexts, particularly in the semiconductor industry,for example to be used in integrated circuits. Such films may be ofinterest for use in, for example, metal gate applications or in otherapplications, like barrier and electrode applications, for example, inintegrated circuits. Deposition of such films with suitable structuraland electrical characteristics for incorporation in semiconductordevices has heretofore proven difficult.

SUMMARY OF THE INVENTION

Processes for depositing titanium aluminum or tantalum aluminum thinfilms comprising nitrogen on a substrate in a reaction space maycomprise at least one deposition cycle. Each cycle may comprisealternately and sequentially contacting the substrate with a vapor phaseTi or Ta precursor and a vapor phase Al precursor. In each cycle atleast one of the vapor phase Ti or Ta precursor and the vapor phase Alprecursor may contact the substrate in the presence of a vapor phasenitrogen precursor.

In some embodiments the Al precursor may comprise an alky or alkenylcompound or a derivative thereof. In some embodiments the Al precursormay comprise an alane, aminealane, or aluminum hydride compound or aderivative thereof. In some embodiments the Al precursor comprisestritertbutylaluminum (TTBA). In some embodiments the Ti or Ta precursorcomprises a halide ligand. In some embodiments the titanium or tantalumprecursor comprises TiCl₄. In some embodiments the titanium or tantalumprecursor comprises TaCl₅. In some embodiments the aluminum precursorcomprises tritertbutylaluminum (TTBA) and the titanium or tantalumprecursor comprises TiCl₄. In some embodiments the aluminum precursorcomprises tritertbutylaluminum (TTBA) and the titanium or tantalumprecursor comprises TaCl₅.

In some embodiments the vapor phase nitrogen precursor is introducedinto the reaction space concurrently with one or both of the Ti or Taprecursor and the Al precursor. In some embodiments the vapor phasenitrogen precursor serves as a carrier gas for one or both of the Ti orTa precursor and the Al precursor. In some embodiments the vapor phasenitrogen precursor comprises N₂.

In some embodiments at least one deposition cycle is carried out at lessthan 500° C. In some embodiments at least one deposition cycle iscarried out at about 300° C. to about 400° C. In some embodiments excessprecursor and reaction byproducts, if any, are removed from the reactionspace after contacting the substrate with the vapor phase Ti or Taprecursor and before subsequently contacting the substrate with thevapor phase Al precursor. In some embodiments the vapor phase nitrogenprecursor flows into the reaction space throughout the deposition cycleand aids in the removal of excess precursor and reaction byproducts, ifany, from the reaction space.

In some embodiments the titanium aluminum or tantalum aluminum thin filmcomprises up to about 40% carbon on an atomic basis. In some embodimentsthe titanium aluminum or tantalum aluminum thin film comprises up toabout 25% nitrogen on an atomic basis. In some embodiments the processis an atomic layer deposition process. In some embodiments at least oneof the reactants at least partially decomposes on the substrate surface.

According to some embodiments a process for depositing a titaniumaluminum thin film comprising nitrogen on a substrate in a reactionspace comprises one or more deposition cycles. Each deposition cycle maycomprise contacting the substrate with a first vapor phase precursorcomprising TiCl₄, removing excess first vapor phase precursor andreaction byproducts, if any, from the substrate, contacting thesubstrate with a second vapor phase precursor comprising TTBA, andremoving excess second vapor phase precursor and reaction byproducts, ifany, from the substrate. In some embodiments at least one of thecontacting the substrate with a first vapor phase precursor comprisingTiCl₄ and contacting the substrate with a second vapor phase precursorcomprising TTBA steps occurs in the presence of a nitrogen precursorcomprising N₂. In some embodiments the one or more deposition cycles arecarried out at about 300° C. to about 400° C.

According to some embodiments a process for depositing a tantalumaluminum thin film comprising nitrogen on a substrate in a reactionspace comprises one or more deposition cycles. Each deposition cycle maycomprise contacting the substrate with a first vapor phase precursorcomprising TaCl₅, removing excess first vapor phase precursor andreaction byproducts, if any, from the substrate, contacting thesubstrate with a second vapor phase precursor comprising TTBA, andremoving excess second vapor phase precursor and reaction byproducts, ifany, from the substrate. In some embodiments at least one of thecontacting the substrate with a first vapor phase precursor comprisingTaCl₅ and contacting the substrate with a second vapor phase precursorcomprising TTBA steps occurs in the presence of a nitrogen precursor. Insome embodiments the one or more deposition cycles are carried out atabout 300° C. to about 400° C.

In some embodiments the titanium aluminum or tantalum aluminum thin filmcomprising nitrogen comprises up to about 25% nitrogen on an atomicbasis. In some embodiments the titanium aluminum or tantalum aluminumthin film comprising nitrogen comprises up to about 40% carbon on anatomic basis. In some embodiments the nitrogen precursor comprising N₂is introduced into the reaction space as a carrier gas for each of thefirst vapor phase precursor comprising TiCl₄ and the second vapor phaseprecursor comprising TTBA.

In some embodiments removing excess second vapor phase precursorcomprising TTBA comprises continuing to flow the nitrogen precursorcomprising N₂ into the reaction space without providing second vaporphase precursor comprising TTBA. In some embodiments removing excessfirst vapor phase precursor comprising TiCl₄ comprises continuing toflow the nitrogen precursor comprising N₂ without providing first vaporphase precursor comprising TiCl₄. In some embodiments a deposition cycleis repeated two or more times to deposit a TiAl film comprising nitrogento a desired thickness. In some embodiments both first vapor phaseprecursor comprising TiCl₄ and the second vapor phase precursorcomprising TTBA contact the substrate in the presence of a nitrogenprecursor comprising N₂ in each deposition cycle.

In some embodiments removing excess second vapor phase precursorcomprising TTBA comprises continuing to flow the nitrogen precursor intothe reaction space without providing second vapor phase precursorcomprising TTBA. In some embodiments removing excess first vapor phaseprecursor comprising TaCl₅ comprises continuing to flow the nitrogenprecursor without providing first vapor phase precursor comprisingTaCl₅. In some embodiments a deposition cycle is repeated two or moretimes to deposit a TaAl film comprising nitrogen to a desired thickness.In some embodiments both first vapor phase precursor comprising TaCl₅and the second vapor phase precursor comprising TTBA contact thesubstrate in the presence of a nitrogen precursor in each depositioncycle.

According to some embodiments a process for depositing a titaniumaluminum thin film comprising nitrogen on a substrate in a reactionspace comprises at least one deposition cycle. In some embodiments thedeposition cycle may comprise contacting the substrate with a firstvapor phase precursor comprising TiCl₄, removing excess first vaporphase precursor and reaction byproducts, if any, from the substrate,contacting the substrate with a second vapor phase precursor comprisingTTBA, and removing excess second vapor phase precursor and reactionbyproducts, if any, from the substrate. In some embodiments at least oneof the contacting the substrate with a first vapor phase precursorcomprising TiCl₄ and contacting the substrate with a second vapor phaseprecursor comprising TTBA steps occurs in the presence of a nitrogenprecursor comprising N₂. In some embodiments the process furthercomprises optionally contacting the substrate with a protectivetreatment reagent comprising a silane or borane. In some embodiments theprocess further comprises optionally repeating at least the first vaporphase precursor and second vapor phase precursor contacting and removingsteps until TiAl thin film comprising nitrogen of the desired thicknesshas been formed.

According to some embodiments a process for depositing a tantalumaluminum thin film comprising nitrogen on a substrate in a reactionspace comprises at least one deposition cycle. In some embodiments thedeposition cycle may comprise contacting the substrate with a firstvapor phase precursor comprising TaCl₅, removing excess first vaporphase precursor and reaction byproducts, if any, from the substrate,contacting the substrate with a second vapor phase precursor comprisingTTBA, and removing excess second vapor phase precursor and reactionbyproducts, if any, from the substrate. In some embodiments at least oneof the contacting the substrate with a first vapor phase precursorcomprising TaCl₅ and contacting the substrate with a second vapor phaseprecursor comprising TTBA steps occurs in the presence of a nitrogenprecursor. In some embodiments the process further comprises optionallycontacting the substrate with a protective treatment reagent comprisinga silane or borane. In some embodiments the process further comprisesoptionally repeating at least the first vapor phase precursor and secondvapor phase precursor contacting and removing steps until TaAl thin filmcomprising nitrogen of the desired thickness has been formed.

In some embodiments the substrate is contacted with a protectivetreatment reagent comprising a silane or borane in each depositioncycle. In some embodiments the silane or borane is selected from thegroup consisting of monosilane, disilane, trisilane, borane, diborane,and triborane. In some embodiments the substrate is contacted with aprotective treatment reagent comprising a silane or borane after every2, 5, 10, 20 or more deposition cycles. In some embodiments the TiAl orTaAl thin film comprising nitrogen comprises from about 5 at % to about50 at % silane or borane. In some embodiments the protective treatmentreagent comprises a vapor phase protective treatment reagent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a flow diagram for a deposition process fordepositing a TiAl or TaAl thin film comprising nitrogen on a substratein a reaction space.

FIG. 2 shows a graph of effective work function (eWF) as a function ofdeposition temperature for exemplary TiAl thin films comprisingnitrogen, as deposited using N₂ as a carrier gas, compared withexemplary TiAl films deposited using Ar as a carrier gas.

FIG. 3 is a schematic cross-sectional side view of an electrodestructure, comprising a TiAl or TaAl thin film comprising nitrogen,according to some embodiments of the invention.

FIG. 4 is a schematic cross-sectional side view of an electrodestructure, comprising an NMOS stack that includes a dielectric layer, afirst metal nitride layer, a titanium aluminum or tantalum aluminumlayer, a second metal nitride layer, and a metal layer, according tosome embodiments of the invention.

FIGS. 5A-C are process flow diagrams generally illustrating protectivetreatment of a TiN layer or a TiAl or TaAl layer during a process forforming a thin film stack in accordance with some embodiments.

DETAILED DESCRIPTION

Titanium aluminum or tantalum aluminum films can be deposited fromaluminum reactants that do not comprise beta hydrogens, such astirtertbutylaluminum (TTBA) and a titanium or tantalum precursor, suchas TiCl₄ in a cyclical deposition process. As described herein, it hasbeen surprisingly found that if the films are deposited in the presenceof nitrogen, such as a molecular nitrogen carrier gas, nitrogen isincorporated into the film, even at relatively low temperatures. In someembodiments, the addition of nitrogen to the film improves one or morefilm properties. For example, the TiAl or TaAl films comprising nitrogendeposited according to the present disclosure may have lower workfunctions than TiAl or TaAl films without nitrogen and at the same timemay have lower resistivities. In some embodiments the resistivity of aTiAl or TaAl film deposited according to the present disclosure is lowerthan the resistivity of a similar metal carbide films, such as TiC.

As used herein, TiAl or TaAl is used for simplicity and is not intendedto limit, restrict, or define the bonding or chemical state, for examplethe oxidation state, of any Ti, Ta, Al, and/or any other elements in thefilm. Further, a TiAl or TaAl film, layer, or material as referred toherein may comprise elements in addition to Ti, Ta, and/or Al. Forexample a TiAl or TaAl film may also comprise nitrogen.

In some embodiments the resistivity of a TiAl or TaAl film deposited isfrom about 3 to about 10⁵ μΩcm as measured from about 10 nm thick films.In some embodiments the resistivity of a TiAl or TaAl film deposited isfrom about 50 to about 10⁴ μΩcm as measured from about 10 nm thickfilms. In some embodiments the resistivity of a TiAl or TaAl filmdeposited is less than about 5×10³ μΩcm, less than about 1000 μΩcm, lessthan about 400 μΩcm as measured from about 10 nm thick films. In someembodiments the resistivity of a TiAl or TaAl film deposited is lessthan about 200 μΩcm as measured from about 10 nm thick films.Resistivity of the film generally varies if the films are thin, in whichcase the resistivity is usually higher, and in case of thicker films theresistivity might be closer bulk or bulk thin film resistivity values.

Titanium aluminum (TiAl) or tantalum aluminum (TaAl) thin filmscomprising nitrogen can be used in a variety of contexts, includingmetal gate and gate electrode applications in metal oxide semiconductorfield effect transistors (MOSFETs), such as n-channel MOSFETs (NMOS).

According to some embodiments, processes for depositing a TiAl or TaAlthin film comprising nitrogen on a substrate in a reaction space caninclude alternately and sequentially contacting the substrate with avapor phase aluminum (Al) precursor and a vapor phase titanium (Ti) ortantalum (Ta) precursor in the presence of a vapor phase nitrogenprecursor.

In some embodiments TiAl or TaAl films comprising nitrogen are depositedby a process comprising one or more deposition cycles, where at leastone deposition cycle comprises alternately and sequentially contacting asubstrate in a reaction space with a vapor phase Al precursor in thepresence of a vapor phase nitrogen precursor, and a Ti or Ta precursorin the presence of a vapor phase nitrogen precursor. The depositioncycle may be repeated two or more times in order to deposit a TiAl orTaAl film comprising nitrogen to a desired thickness. In someembodiments the deposition process is an ALD type process.

In some embodiments nitrogen may be incorporated from a nitrogenprecursor, for example N₂, into a deposited TiAl or TaAl thin film. Insome embodiments nitrogen may be incorporated into a deposited TiAl orTaAl thin film from, for example, a carrier gas comprising a nitrogenprecursor, for example an N₂ carrier gas. In some embodiments wherenitrogen is incorporated from a nitrogen precursor into the depositedTiAl or TaAl thin films, certain properties of the films, for exampleeWF, may be different than in TiAl or TaAl films deposited by a processthat does not include a nitrogen precursor. For example, in someembodiments where nitrogen is incorporated from a carrier gas comprisinga nitrogen precursor into a deposited TiAl or TaAl thin film the eWF ofthe film may be lower than in a TiAl or TaAl film deposited using acarrier gas that does not comprise nitrogen, for example an Ar or otherinert carrier gas. For example, a TiAl or TaAl film comprising nitrogenincorporated from a carrier gas comprising a nitrogen precursor may havean eWF more than about 5 mV lower, more than about 50 mV lower, or morethan about 100 mV lower than in a TiAl or TaAl film deposited by aprocess using a carrier gas that comprises Ar or another inert carriergas and that does not comprise a nitrogen precursor.

ALD Type Processes

ALD type processes are based on controlled, self-limiting surfacereactions of precursor chemicals. Gas phase reactions are avoided byalternately and sequentially contacting the substrate with theprecursors. Vapor phase reactants are separated from each other on thesubstrate surface, for example, by removing excess reactants and/orreactant byproducts from the reaction chamber between reactant pulses.In some embodiments one or more substrate surfaces are alternately andsequentially contacted with two or more vapor phase precursors, orreactants. Contacting a substrate surface with a vapor-phase reactantmeans that the reactant vapor is in contact with the substrate surfacefor a limited period of time. In other words, it can be understood thatthe substrate surface is exposed to each vapor phase reactant for alimited period of time.

Briefly, a substrate is heated to a suitable deposition temperature,generally at lowered pressure. Deposition temperatures are generallymaintained below the thermal decomposition temperature of the reactantsbut at a high enough level to avoid condensation of reactants and toprovide the activation energy for the desired surface reactions. Ofcourse, the appropriate temperature window for any given ALD reactionwill depend upon the surface termination and reactant species involved.Here, the temperature varies depending on the precursors being used andis preferably at or below about 500° C., preferably between about 250°C. and about 500° C., more preferably between about 275° C. and about450° C., more preferably between about 300° C. and about 425° C., andmost preferably between about 300° C. and about 400° C.

The surface of the substrate is contacted with a vapor phase firstreactant. In some embodiments a pulse of vapor phase first reactant isprovided to a reaction space containing the substrate. In someembodiments the substrate is moved to a reaction space containing vaporphase first reactant. Conditions are preferably selected such that nomore than about one monolayer of the first reactant is adsorbed on thesubstrate surface in a self-limiting manner. The appropriate contactingtimes can be readily determined by the skilled artisan based on theparticular circumstances. Excess first reactant and reaction byproducts,if any, are removed from the substrate surface, such as by purging withan inert gas or by removing the substrate from the presence of the firstreactant.

Purging means that vapor phase precursors and/or vapor phase byproductsare removed from the substrate surface such as by evacuating a chamberwith a vacuum pump and/or by replacing the gas inside a reactor with aninert gas such as argon or nitrogen. Typical purging times are fromabout 0.05 to 20 seconds, more preferably between about 1 and 10, andstill more preferably between about 1 and 2 seconds. However, otherpurge times can be utilized if necessary, such as where highly conformalstep coverage over extremely high aspect ratio structures or otherstructures with complex surface morphology is needed.

In some embodiments purging may be accomplished by shutting off the flowof precursor while continuing to flow a carrier gas. Thus, in someembodiments, the deposition cycle may comprise alternately andsequentially providing the Al precursor and Ti or Ta precursor into acontinually flowing carrier gas. In some embodiments the carrier gascomprises nitrogen, such as molecular nitrogen.

The surface of the substrate is contacted with a vapor phase secondgaseous reactant. In some embodiments a pulse of a second gaseousreactant is provided to a reaction space containing the substrate. Insome embodiments the substrate is moved to a reaction space containingthe vapor phase second reactant. Excess second reactant and gaseousbyproducts of the surface reaction, if any, are removed from thesubstrate surface. The steps of contacting and removing are repeateduntil a thin film of the desired thickness has been selectively formedon the first surface of substrate, with each cycle leaving no more thanabout a molecular monolayer. Additional phases comprising alternatelyand sequentially contacting the surface of a substrate with otherreactants can be included to form more complicated materials, such asternary materials.

As mentioned above, each phase of each cycle is preferablyself-limiting. An excess of reactant precursors is supplied in eachphase to saturate the susceptible structure surfaces. Surface saturationensures reactant occupation of all available reactive sites (subject,for example, to physical size or “steric hindrance” restraints) and thusensures excellent step coverage. Typically, less than one molecularlayer of material is deposited with each cycle, however, in someembodiments more than one molecular layer is deposited during the cycle.

Removing excess reactants can include evacuating some of the contents ofa reaction space and/or purging a reaction space with helium, nitrogenor another inert gas. In some embodiments purging can comprise turningoff the flow of the reactive gas while continuing to flow an inertcarrier gas to the reaction space.

The precursors employed in the ALD type processes may be solid, liquidor gaseous materials under standard conditions (room temperature andatmospheric pressure), provided that the precursors are in vapor phasebefore they are contacted with the substrate surface. Contacting asubstrate surface with a vaporized precursor means that the precursorvapor is in contact with the substrate surface for a limited period oftime. Typically, the contacting time is from about 0.05 to 10 seconds.However, depending on the substrate type and its surface area, thecontacting time may be even higher than 10 seconds. Contacting times canbe on the order of minutes in some cases. The optimum contacting timecan be determined by the skilled artisan based on the particularcircumstances.

The mass flow rate of the precursors can also be determined by theskilled artisan. In some embodiments the flow rate of metal precursorsis preferably between about 1 and 1000 sccm without limitation, morepreferably between about 100 and 500 sccm.

The pressure in a reaction chamber is typically from about 0.01 to about20 mbar, more preferably from about 1 to about 10 mbar. However, in somecases the pressure will be higher or lower than this range, as can bedetermined by the skilled artisan given the particular circumstances.

Before starting the deposition of the film, the substrate is typicallyheated to a suitable growth temperature. The growth temperature variesdepending on the type of thin film formed, physical properties of theprecursors, etc. The growth temperatures are discussed in greater detailbelow in reference to each type of thin film formed. The growthtemperature can be less than the crystallization temperature for thedeposited materials such that an amorphous thin film is formed or it canbe above the crystallization temperature such that a crystalline thinfilm is formed. The deposition temperature may vary depending on anumber of factors such as, and without limitation, the reactantprecursors, the pressure, flow rate, the arrangement of the reactor,crystallization temperature of the deposited thin film, and thecomposition of the substrate including the nature of the material to bedeposited on. The specific growth temperature may be selected by theskilled artisan.

Reactors capable of being used to grow thin films can be used for thedeposition. Such reactors include ALD reactors, as well as CVD reactorsequipped with appropriate equipment and means for providing theprecursors. According to some embodiments, a showerhead reactor may beused.

Examples of suitable reactors that may be used include commerciallyavailable equipment such as the F-120® reactor, F-450® reactor, Pulsar®reactors—such as the Pulsar® 2000 and the Pulsar® 3000—EmerALD® reactorand Advance® 400 Series reactors, available from ASM America, Inc ofPhoenix, Ariz. and ASM Europe B.V., Almere, Netherlands. Othercommercially available reactors include those from ASM Japan K.K (Tokyo,Japan) under the tradename Eagle® XP and XP8.

In some embodiments a batch reactor may be used. Suitable batch reactorsinclude, but are not limited to, reactors commercially available fromand ASM Europe B.V (Almere, Netherlands) under the trade names ALDA400™and A412™. In some embodiments a vertical batch reactor is utilized inwhich the boat rotates during processing, such as the A412™. Thus, insome embodiments the wafers rotate during processing. In someembodiments in which a batch reactor is used, wafer-to-wafer uniformityis less than 3% (1sigma), less than 2%, less than 1% or even less than0.5%.

The growth processes can optionally be carried out in a reactor orreaction space connected to a cluster tool. In a cluster tool, becauseeach reaction space is dedicated to one type of process, the temperatureof the reaction space in each module can be kept constant, whichimproves the throughput compared to a reactor in which the substrate isheated up to the process temperature before each run.

A stand-alone reactor can be equipped with a load-lock. In that case, itis not necessary to cool down the reaction space between each run.

Preferably, for forming a TiAl or TaAl thin film comprising nitrogen,each ALD cycle comprises at least two distinct phase. Contacting thesubstrate with a first precursor and thereafter removing excess firstprecursor and reaction byproducts from the substrate surface may beconsidered a phase and may be referred to as a first phase, firstprecursor phase, Ti or Ta phase, Ti or Ta precursor phase, first Ti orTa phase, and/or first Ti or Ta precursor phase. For a deposition cycle,in a first phase, the substrate is contacted with a first precursorcomprising Ti or Ta, which forms no more than about one monolayer on thesubstrate surface. In a second phase, the substrate is contacted with asecond precursor comprising Al and may convert adsorbed first reactantspecies to a titanium aluminum material. Contacting the substrate with asecond precursor and thereafter removing excess second precursor andreaction byproducts from the substrate surface may be considered a phaseand may be referred to as a second phase, second precursor phase, Alphase, Al precursor phase, first Al phase, and/or first Al precursorphase. One or more of the precursors may be provided with the aid of acarrier gas, such as N₂, Ar, or He. Additional phases may be added andphases may be removed as desired to adjust the composition of the finalfilm.

As mentioned above, in some embodiments a nitrogen precursor is presentin the reaction space during both the time that the substrate iscontacted with the Al precursor and the time that the substrate iscontacted with the Ti or Ta precursor. In some embodiments the nitrogenprecursor is present in the reaction space when the substrate iscontacted with the Al precursor but not when the substrate is contactedwith the Ti or Ta precursor. In some embodiments the nitrogen precursoris present in the reaction space when the substrate is contacted withthe Ti or Ta precursor but not when the substrate is contacted with theAl precursor.

In some embodiments the nitrogen precursor is flowed continuously to thereaction space during the entire deposition cycle, while in someembodiments the nitrogen precursor may be present in the reaction spaceduring the time that the Al precursor and/or the Ti or Ta precursor arepresent. Thus, in some embodiments the nitrogen precursor may beprovided at the same time as one or both of the Al and/or Ti or Taprecursors. For example, in some embodiments a carrier gas comprisingthe nitrogen precursor may also be used to provide the Al and/or Ti orTa precursors. In some embodiments the nitrogen precursor, for exampleN₂, may be provided into the reaction space at a different time than oneor both of the Al and/or Ti or Ta precursors. In some embodiments thenitrogen precursor, for example N₂, may be provided into the reactionspace at separate time than one or both of the Al and/or Ti or Taprecursors.

In some embodiments, vapor phase nitrogen precursor flows into thereaction space throughout the deposition cycle and can aid in theremoval of excess Al and/or Ti or Ta precursor and reaction byproducts,if any, from the reaction space. In some embodiments, excess Alprecursor can be removed from the reaction space by continuing to flowvapor phase nitrogen precursor into the reaction space without providingAl precursor. Additionally, excess Ti or Ta precursor can be removedfrom the reaction space by continuing to flow vapor phase nitrogenprecursor into the reaction space without providing Ti or Ta precursor.

In some embodiments, the vapor phase nitrogen precursor is used as acarrier gas for one of or both of the Al and Ti or Ta precursors. Inother embodiments, the vapor phase nitrogen precursor can be introducedinto the reaction space through a gas flow separate from the one of orboth of the vapor phase Al and Ti or Ta precursors. Additionally, insome embodiments, the vapor phase nitrogen precursor may be present inthe reaction space while one of or both of the Al or Ti or Ta precursorsare contacting the substrate.

Referring to FIG. 1 and according to some embodiments a TiAl or TaAlthin film comprising nitrogen is deposited on a substrate in a reactionspace by an ALD type deposition process 100 comprising at least onecycle comprising:

contacting the substrate with a first vapor phase precursor comprisingTi or Ta at step 120;

removing excess first precursor and reaction by products, if any, fromthe substrate at step 130;

contacting the substrate with a second vapor phase precursor comprisingAl at step 140;

removing from the substrate, at step 150, excess second precursor andany gaseous by-products;

wherein at least one of the contacting the substrate with a first vaporphase precursor comprising Ti or Ta and contacting the substrate with asecond vapor phase precursor comprising Al steps occurs in the presenceof a nitrogen precursor; and

optionally repeating at step 160 the contacting and removing steps untilTiAl or TaAl thin film comprising nitrogen of the desired thickness hasbeen formed.

In some embodiments both of the contacting the substrate with a firstvapor phase precursor comprising Ti or Ta and contacting the substratewith a second vapor phase precursor comprising Al steps occur in thepresence of a nitrogen precursor.

Referring again to FIG. 1, the substrate is contacted with a firstprecursor comprising Ti or Ta at step 120. In some embodiments the firstprecursor is conducted into a reaction chamber in the form of vaporphase pulse and contacted with the surface of the substrate. Conditionsare preferably selected such that no more than about one monolayer ofthe precursor is adsorbed on the substrate surface in a self-limitingmanner. However, in some embodiments conditions may be selected suchthat more than one monolayer of the precursor may be formed.

According to some embodiments a TiAl or TaAl thin film is deposited on asubstrate in a reaction space by an ALD type deposition processcomprising at least one cycle comprising:

Exposing the substrate to a first vapor phase precursor comprising Ti orTa;

Exposing the substrate to a purge gas and/or removing excess firstprecursor and reaction by products, if any, from the substrate;

Exposing the substrate to a second vapor phase precursor comprising Al;

Exposing the substrate to a purge gas and/or removing excess secondprecursor and reaction by products, if any, from the substrate; and

optionally repeating at the exposing and/or removing steps until TiAl orTaAl thin film of the desired thickness has been formed.

In some embodiments one or both of the exposing the substrate to a firstvapor phase precursor comprising Ti or Ta and exposing the substrate toa second vapor phase precursor comprising Al steps occurs in thepresence of a nitrogen precursor. In some embodiments the step ofexposing the substrate to a first vapor phase precursor comprising Ti orTa comprises exposing the substrate to a mixture of Ti and/or Taprecursors. In some embodiments the step of exposing the substrate to asecond vapor phase precursor comprising Al comprises exposing thesubstrate to a mixture of Al precursors.

In some embodiments the nitrogen precursor may comprise the purge gas.

In some embodiments the step of exposing the substrate to a first vaporphase precursor comprising Ti or Ta and the step of exposing thesubstrate to a purge gas and/or removing excess second precursor andreaction by products, if any, from the substrate; is repeated more thanone time, more than two times, more than 3, 5 or 10 times beforeexposing the substrate to a second vapor phase precursor comprising Al.In some embodiments when the step of exposing the substrate to a firstvapor phase precursor comprising Ti or Ta is repeated more than one timethe Ti or Ta precursor maybe independently selected to be same ordifferent in the repeated exposing steps.

In some embodiments the step of exposing the substrate to a second vaporphase precursor comprising Al and the step of exposing the substrate toa purge gas and/or removing excess second precursor and reaction byproducts, if any, from the substrate; is repeated more than one time,more than two times, more than 3, 5 or 10 times before exposing thesubstrate to a first vapor phase precursor comprising Ti or Ta. In someembodiments when the step of exposing the substrate to a first vaporphase precursor comprising Al is repeated more than one time the Alprecursor maybe independently selected to be same or different in therepeated exposing steps.

The first precursor pulse is preferably supplied in gaseous form. Thefirst precursor gas is considered “volatile” for purposes of the presentdescription if the species exhibits sufficient vapor pressure under theprocess conditions to transport the species to the workpiece insufficient concentration to saturate exposed surfaces.

In some embodiments the first precursor contacts the substrate for about0.01 seconds to about 60 seconds, for about 0.02 seconds to about 30seconds, for about 0.025 seconds to about 20 seconds, for about 0.05seconds to about 5.0 seconds, about 0.05 seconds to about 2.0 seconds orabout 0.1 seconds to about 1.0 second.

The first precursor employed in the ALD type processes may be solid,liquid, or gaseous material under standard conditions (room temperatureand atmospheric pressure), provided that the first precursor is in vaporphase before it is conducted into the reaction chamber and contactedwith the substrate surface.

In some embodiments the first precursor optionally contacts thesubstrate in the presence of a nitrogen precursor. In some embodimentsthe first precursor is conducted into a reaction chamber with the aid ofa carrier gas that comprises a nitrogen precursor, for example molecularnitrogen. In some embodiments a vapor phase nitrogen precursor can beintroduced into the reaction space through a separate gas flow from thefirst precursor.

At step 130 excess first precursor and reaction byproducts, if any, areremoved from the substrate surface, for example by purging with a pulseof inert gas such as nitrogen or argon. Purging the reaction chambermeans that vapor phase precursors and/or vapor phase byproducts areremoved from the reaction chamber such as by evacuating the chamber witha vacuum pump and/or by replacing the gas inside the reactor with aninert gas such as argon or nitrogen. Typical purging times are fromabout 0.05 to 20 seconds, more preferably between about 1 and 10seconds, and still more preferably between about 1 and 2 seconds.However, other purge times can be utilized if necessary, such as whendepositing layers over extremely high aspect ratio structures or otherstructures with complex surface morphology is needed. The appropriatepurging times can be readily determined by the skilled artisan based onthe particular circumstances.

In some embodiments purging may be accomplished by shutting off the flowof precursor while continuing to flow a carrier gas. Thus, In someembodiments removing excess first precursor and reaction byproducts, ifany, may comprise stopping the flow of first precursor while continuingto flow a carrier gas, for example a gas comprising a nitrogenprecursor. In some embodiments the carrier gas comprises a nitrogenprecursor, such as molecular nitrogen.

In other embodiments however, removing excess first precursor andreaction byproducts, if any, may comprise moving the substrate so thatthe first precursor no longer contacts the substrate. In someembodiments no precursor may be removed from the various parts of achamber. In some embodiments the substrate is moved from a part of thechamber containing a first precursor to another part of the chambercontaining a second precursor or no precursor at all. In someembodiments the substrate is moved from a first reaction chamber to asecond, different reaction chamber.

At step 140 the substrate is contacted with a second vapor phaseprecursor comprising Al. In some embodiments the second precursor ispulsed into the chamber where it reacts with the first precursor boundto the first surface of the substrate. The reaction typically forms upto about a monolayer of TiAl or TaAl material comprising nitrogen on thesubstrate. In some embodiments, however, more than one molecular layerof TiAl or TaAl material comprising nitrogen is formed on the substrate.

In some embodiments the second precursor optionally contacts thesubstrate in the presence of a nitrogen precursor. In some embodimentsthe second precursor is conducted into a reaction chamber with the aidof a carrier gas that comprises a nitrogen precursor, for examplemolecular nitrogen. In some embodiments a vapor phase nitrogen precursorcan be introduced into the reaction space through a separate gas flowfrom the second precursor.

While one skilled in the art will recognize that any number of suitablesecond precursors may be used, appropriate second precursors include Alcontaining compounds that favorably react with the ligands of apreviously or subsequently deposited first precursor. Accordingly,selection of an appropriate second precursor may depend on the specificfirst precursor used and the nature of the ligands in the firstprecursor. Typically, a second precursor is utilized that comprises asingle vapor phase Al precursor. However, in some embodiments, a secondprecursor may comprise two or more Al precursors. In some embodiments asecond precursor may comprise one primary aluminum precursor and one ormore additional aluminum precursors, for example as contaminants orminor components thereof.

In some embodiments the second precursor contacts the substrate forabout 0.01 seconds to about 60 seconds, for about 0.02 seconds to about30 seconds, for about 0.025 seconds to about 20 seconds, for about 0.05seconds to about 5.0 seconds, about 0.05 seconds to about 2.0 seconds orabout 0.1 seconds to about 1.0 second. However, depending on the reactortype, substrate type and its surface area, the second precursorcontacting time may be even higher than 10 seconds. In some embodiments,contacting times can be on the order of minutes. The optimum contactingtime can be readily determined by the skilled artisan based on theparticular circumstances.

The concentration of the second precursor in the reaction chamber may befrom about 0.01% by volume to about 99.0% or up to 100% by volume. Andthe second precursor may flow through the reaction chamber at a rate ofbetween about 1 standard cm³/min and about 4000 standard cm³/min.

At step 150, excess second precursor and gaseous by-products of thesurface reaction, if any, are removed from the substrate, as describedabove for step 130. In some embodiments excess precursor and reactionbyproducts are preferably removed with the aid of an inert gas.

The steps of contacting and removing may be optionally repeated at step160 TiAl or TaAl thin film comprising nitrogen of a desired thicknesshas been formed on the first surface of the substrate, with each cycleleaving no more than about a molecular monolayer. In some cases, itmight be desirable to achieve at least partial decomposition of at leastone the various precursors. Thus, in some embodiments conditions may beselected such that more than one molecular layer of a TiAl or TaAlmaterial comprising nitrogen is formed on the substrate in eachdeposition cycle.

The ALD processes of the present disclosure may comprise one or morecycles. Some embodiments involve the repetition of at least about 5cycles, at least about 10 cycles, or at least about 50 cycles. In someembodiments, no more than 100 cycles are performed to form a thin filmof a desirable thickness.

Although the illustrated deposition cycle for forming a TiAl or TaAlthin film comprising nitrogen begins with contacting the surface of thesubstrate with the first vapor phase precursor comprising Ti or Ta, inother embodiments the deposition cycle begins with contacting thesurface of the substrate with the second vapor phase precursorcomprising Al. It will be understood by the skilled artisan thatcontacting the substrate surface with the first vapor phase precursorcomprising Ti or Ta and second vapor phase precursor comprising Al areinterchangeable in the deposition cycle.

In some embodiments the substrate is moved such that different reactantsalternately and sequentially contact the surface of the substrate in adesired sequence for a desired time. In some embodiments the removingsteps, 130 and 150 are not performed. In some embodiments no reactantmay be removed from the various parts of a chamber. In some embodimentsthe substrate is moved from a part of the chamber containing a firstprecursor to another part of the chamber containing the second reactant.In some embodiments the substrate is moved from a first reaction chamberto a second, different reaction chamber.

The skilled artisan can determine the optimal reactant evaporationtemperatures based on the properties of the selected precursors. Theskilled artisan can determine the optimal reactant contact times throughroutine experimentation based on the properties of the selectedprecursors and the desired properties of the deposited TiAl or TaAl thinfilm, for example a TiAl or TaAl thin film comprising nitrogen.

The growth rate of the TiAl or TaAl thin films, for example TiAl or TaAlthin films comprising nitrogen, will vary depending on the reactionconditions. In some embodiments the growth rate may be from about 0.01Å/cycle to about 10.0 Å/cycle, preferably from about 0.1 Å/cycle toabout 5 Å/cycle, more preferably 0.3 Å/cycle to about 3.0 Å/cycle. Insome embodiments the growth rate may is about 2.5 Å/cycle. In someembodiments the growth rate may be more than about 2 Å/cycle, more thanabout 3 Å/cycle, more than about 5 Å/cycle or more than about 10Å/cycle, for example, in cases where some decomposition of the precursormay occur the deposition rate may increase without substantial limitwhen the pulse time is increased.

In some embodiments of the invention, the deposition process is carriedout at a temperature of less than about 600° C., temperature of lessthan about 550° C., temperature of less than about 500° C. In otherembodiments, the deposition process is carried out at a temperature ofbetween about 250° C. to about 500° C., between about 300° C. to about450° C., between about 350° C. to about 450° C. or between about 375° C.to about 425° C.

In some embodiments, the deposited TiAl or TaAl thin film, for exampleTiAl or TaAl thin films comprising nitrogen, may contain up to about 30%to about 40% carbon on an atomic basis (at-%). In some embodiments theTiAl or TaAl thin film may comprise carbon from about 2% to about 60%,from about 5% to about 55%, from about 10% to about 50%, from about 20%to about 45%, from about 35% to about 45% on atomic basis. In someembodiments the TiAl or TaAl thin film may comprise carbon up to about60% or up to about 50% on atomic basis. In some embodiments the TiAl orTaAl thin film may comprise carbon from at least about 2% to at leastabout 20% on atomic basis. In some embodiments the TiAl or TaAl thinfilm may comprise up to about 20% to about 25% nitrogen on an atomicbasis, with the nitrogen being incorporated from the vapor phasenitrogen precursor. In some embodiments the TiAl or TaAl thin film maycomprise up to from about 0.1% to about 30%, from about 2 to about 25%nitrogen on an atomic basis, with the nitrogen being incorporated fromthe vapor phase nitrogen precursor. In some embodiments the TiAl or TaAlthin film may comprise more than about 1%, more than about 5%, more thanabout 10%, more than about 15% on atomic basis, with the nitrogen beingincorporated from the vapor phase nitrogen precursor.

In some embodiments, the deposited TiAl thin film comprises Ti fromabout 1% to about 55%, from about 20% to about 55%, from about 30% toabout 50%, from about 25% to about 35%, from about 27% to about 33% onatomic basis. In some embodiments, the deposited TiAl thin filmcomprises Ti at least about 10%, at least about 25%, at least about 30%on atomic basis.

In some embodiments, the deposited TiAl thin film comprises Al fromabout 5% to about 75%, from about 7.5% to about 60, from about 10% toabout 45%, from about 10% to about 40%, from about 10% to about 20% onatomic basis. In some embodiments, the deposited TiAl thin filmcomprises Al at least about 10%, at least about 25% or at least about35% on atomic basis.

In some embodiments, the deposited TaAl thin film comprises Ta fromabout 1% to about 55%, from about 20% to about 55%, from about 30% toabout 50%, from about 25% to about 35%, from about 27% to about 33% onatomic basis. In some embodiments, the deposited TaAl thin filmcomprises Ta at least about 10%, at least about 25%, at least about 30%on atomic basis.

In some embodiments, the deposited TaAl thin film comprises Al fromabout 5% to about 75%, from about 7.5% to about 60, from about 10% toabout 45%, from about 10% to about 40%, from about 10% to about 20% onatomic basis. In some embodiments, the deposited TaAl thin filmcomprises Al at least about 10%, at least about 25% or at least about35% on atomic basis.

In some embodiments, the vapor phase first precursor comprising Ti or Tacomprises TiCl₄, the vapor phase second precursor comprising Alcomprises tritertbutylaluminum (TTBA), and the vapor phase nitrogenprecursor comprises N₂.

Thus according to some embodiments a TiAl thin film comprising nitrogenis deposited on a substrate in a reaction space by an ALD typedeposition process comprising at least one cycle comprising:

contacting the substrate with a first vapor phase precursor comprisingTiCl₄;

removing excess first precursor and reaction by products, if any, fromthe substrate;

contacting the substrate with a second vapor phase precursor comprisingTTBA;

removing from the substrate excess second precursor and any gaseousby-products;

wherein at least one of the contacting the substrate with a first vaporphase and contacting the substrate with a second vapor phase precursorsteps occurs in the presence of a nitrogen precursor comprising N₂; and

optionally repeating the contacting and removing steps until TiAl thinfilm comprising nitrogen of the desired thickness has been formed.

Thus according to some embodiments a TaAl thin film comprising nitrogenis deposited on a substrate in a reaction space by an ALD typedeposition process comprising at least one cycle comprising:

contacting the substrate with a first vapor phase precursor comprisingTaCl₅;

removing excess first precursor and reaction by products, if any, fromthe substrate;

contacting the substrate with a second vapor phase precursor comprisingTTBA;

removing from the substrate excess second precursor and any gaseousby-products;

wherein at least one of the contacting the substrate with a first vaporphase precursor and contacting the substrate with a second vapor phaseprecursor steps occurs in the presence of a nitrogen precursor; and

optionally repeating the contacting and removing steps until TiAl thinfilm comprising nitrogen of the desired thickness has been formed.

In some embodiments a TiAl thin film comprising nitrogen is deposited ona substrate in a reaction space by a cyclical deposition processcomprising at least one deposition cycle comprising alternately andsequentially contacting the substrate with TTBA and TiCl₄, wherein atleast one of TTBA and/or TiCl₄ contacts the substrate in the presence ofN₂.

In some embodiments a TaAl thin film comprising nitrogen is deposited ona substrate in a reaction space by a cyclical deposition processcomprising at least one deposition cycle comprising alternately andsequentially contacting the substrate with TTBA and TaCl₅, wherein atleast one of TTBA and/or TiCl₄ contacts the substrate in the presence ofa nitrogen precursor.

Ti Precursors

In some embodiments a precursor is utilized that comprises a singlevapor phase Ti precursor. However, in some embodiments, a Ti precursormay comprise two or more Ti precursors. In some embodiments a Tiprecursor may comprise one primary Ti precursor and one or moreadditional Ti precursors, for example as contaminants or minorcomponents thereof. In some embodiments a Ti precursor comprises TiCl₄.In some embodiments the Ti precursor in a Ti precursor consistsessentially of TiCl₄.

In some embodiments a Ti precursor comprises at least one halide ligand.In some embodiments the Ti precursor has at least one Cl-ligand. In someembodiments a vapor phase Ti precursor may be TiCl₄.

In some embodiments a Ti precursor comprising both Ta and Ti precursorsmay be used.

Ta Precursors

In some embodiments a precursor is utilized that comprises a singlevapor phase Ta precursor. However, in some embodiments, a Ta precursormay comprise two or more Ta precursors. In some embodiments a Taprecursor may comprise one primary Ta precursor and one or moreadditional Ta precursors, for example as contaminants or minorcomponents thereof. In some embodiments a Ta precursor comprises TaCl₅.In some embodiments the Ta precursor in a Ti precursor consistsessentially of TaCl₅.

In some embodiments a Ta precursor comprises at least one halide ligand.In some embodiments the Ta precursor has at least one Cl-ligand. In someembodiments a vapor phase Ta precursor may be TaCl₅.

In some embodiments a Ta precursor comprising both Ta and Ti precursorsmay be used.

Al Precursors

In some embodiments a precursor is utilized that comprises a singlevapor phase Al precursor. However, in some embodiments, an Al precursormay comprise two or more Al precursors. In some embodiments an Alprecursor may comprise one primary Al precursor and one or moreadditional Al precursors, for example as contaminants or minorcomponents thereof. In some embodiments the vapor phase Al precursor maycomprise at least one C4-ligand, such as a C4-alkyl ligand liketertbutyl. In some embodiments the vapor phase Al precursor may betritertbutylaluminum (TTBA). In some embodiments the aluminum precursorconsists essentially of TTBA. In some embodiments the aluminum precursorhas a purity of more than about 99%, more than about 99.9%, more thanabout 99.99%, more than about 99.999% or close to about 100%.

In some embodiments the vapor phase Al precursor may comprise an alane,aminealane or aluminum hydride compound or a derivative thereof. In someembodiments the vapor phase Al precursor does not comprise an Al—H bond.In some embodiments the vapor phase Al precursor does not comprise anisobutyl-ligand. In some embodiments the vapor phase Al precursor doesnot comprise tri-isobutylaluminum (TIBA).

In some embodiments the vapor phase Al precursor may comprise an alkylor alkenyl compound, such as an aluminum allyl compound, analkylaminealane or alkyl aluminum hydride compound or a derivativethereof.

In some embodiments the vapor phase Al precursor may comprise an alkylor alkenyl aluminum compound with one or more C3-C7 ligands, preferablyC4-C5 ligands, such as butyl or pentyl ligands or derivatives thereof,like 2-methylbutyl ligands.

In some embodiments the vapor phase Al precursor may be selected from:trimethylaluminum (TMA), triethylaluminum (TEA), dimethylaluminumhydride (DMAH), dimethylethylaminealane (DMEAA), trimethylaminealane(TEAA), N-methylpyrroridine-alane (MPA), tri-isobutylaluminum (TIBA).

In some embodiments a vapor phase Al precursor may comprise one or moreof the following Al precursors: tritertbutylaluminum (TTBA),trimethylaluminum (TMA), triethylaluminum (TEA), dimethylaluminumhydride (DMAH), dimethylethylaminealane (DMEAA), trimethylaminealane(TEAA), N-methylpyrroridine-alane (MPA), tri-isobutylaluminum (TIBA).

Nitrogen Precursors

In some embodiments a vapor phase nitrogen precursor, or reactant, isutilized that comprises a single vapor phase nitrogen precursor.However, in some embodiments a nitrogen reactant may comprise two ormore nitrogen precursors. In some embodiments a nitrogen reactant maycomprise one primary nitrogen precursor and one or more additionalnitrogen precursors, for example as contaminants or minor componentsthereof. In some embodiments the vapor phase nitrogen reactant comprisesmolecular nitrogen. In some embodiments the nitrogen precursor in avapor phase nitrogen reactant consists essentially of molecularnitrogen. In some embodiments the nitrogen precursor does not compriseNH₃ or another nitrogen precursor having an N—H bond. In someembodiments the nitrogen precursor does not comprise hydrogen. In someembodiments the nitrogen precursor does not comprise plasma, radicals oratomic species (single atoms). In some embodiments the nitrogenprecursor does not comprise nitrogen plasma, nitrogen radicals or atomicnitrogen (single N atoms). In some embodiments the nitrogen precursorcomprises nitrogen atoms which are bonded together. In some embodimentsthe nitrogen precursor comprises nitrogen atoms which are bondedtogether with triple bond.

In some embodiments the vapor phase nitrogen precursor may be molecularnitrogen. In some embodiments the vapor phase nitrogen precursor may beselected from N₂, NH₃, hydrazine, and hydrazine derivatives thereof.

In some embodiments of the invention, the vapor phase Al precursorcomprises tritertbutylaluminum (TTBA), the vapor phase Ti or Taprecursor comprises TiCl₄, and the vapor phase nitrogen precursorcomprises N₂. Thus, in some embodiments a deposition cycle comprisesalternately and sequentially contacting the substrate with TTBA andTiCl₄ in the presence of N₂. In some embodiments N₂ reacts with otherspecies, such as, but not limited to, Ti- or Al-species, on thesubstrate at reaction temperatures lower than 700° C., lower than 600°C., lower than 500° C., or lower than 450° C. In some embodiments the N₂may react with other species and may leave nitrogen in the depositedfilm. In some embodiments a vapor phase nitrogen precursor comprises N₂and has a purity of more than 99.999%, more than 99.9999%, more than99.99999% or more than 99.999999%. In some embodiments vapor phasenitrogen precursor comprises N₂ and is also used as carrier gas and hasa purity of more than 99.999%, more than 99.9999%, more than 99.99999%or more than 99.999999%.

Example 1

TiAl thin films comprising nitrogen were deposited by a plurality ofdeposition cycles. Each cycle comprised contacting a substrate in areaction space with TTBA by introducing vapor phase TTBA into thereaction space with a N₂ carrier gas, purging the reaction space ofexcess TTBA and reaction by products, if any, by stopping the flow ofTTBA and continuing the flow of N₂ into the reaction space, contactingthe substrate with TiCl₄ by introducing vapor phase TiCl₄ into thereaction space with a N₂ carrier gas, and purging the reaction space ofexcess TiCl₄ and reaction byproducts, if any, by stopping the flow ofTiCl₄ and continuing the flow of N₂ into the reaction space.

The TiAl films comprising nitrogen were deposited at a temperature ofbetween 350° C. and 450° C. The effective work function (eWF) of theTiAl films comprising nitrogen ranged from about 4.50 eV to about 4.20eV, depending on the TTBA dose as shown in FIG. 2. TiAl thin films werealso deposited by a deposition process similar to the one described inthe above paragraph, with air replacing N₂ in the deposition cycle.Again, the TiAl films were deposited at a temperature of between 350° C.and 450° C. The eWF of the TiAl films ranged from about 4.60 eV to about4.35 eV as shown in FIG. 2, depending on the TTBA dose. The resultsachieved show that use of N₂ as a carrier gas resulted in a lower eWFfor a film, as compared to using Ar as a carrier gas across a range oftemperatures less than 500° C.

The results achieved show that TiAl films comprising nitrogen haveproperties that are desirable for use in NMOS transistors.

Semiconductor Device Applications

The TiAl or TaAl thin films formed by the processes disclosed herein canbe utilized in a variety of contexts, such as in the formation ofelectrode structures. In some embodiments. The TiAl or TaAl thin filmsused in semiconductor device applications comprise nitrogen. FIG. 3illustrates an exemplary structure. Although described in terms ofseveral specific contexts, one of skill in the art will recognize thatthe processes described herein are applicable to many other contexts aswell.

The deposition processes disclosed herein may be successfully applied tofabricate NMOS transistors including planar devices as well as multiplegate transistors, such as FinFETs.

In some embodiments an electrode is formed by deposition of a TiAl orTaAl layer. With reference to FIG. 3, a layer of high-k dielectricmaterial 300 is deposited onto a substrate (not shown). The substratemay be treated prior to deposition of the high-k material. For example,in some embodiments, a thin interfacial layer (not shown) may bedeposited prior to deposition of the high-k material. In one embodimenta thin chemical oxide or oxynitride is formed on the surface. In otherembodiments a thermal oxide is grown on the substrate.

“High-k” generally refers to a dielectric material having a dielectricconstant (k) value greater than that of silicon oxide. Preferably, thehigh-k material has a dielectric constant greater than 5, morepreferably greater than about 10. Exemplary high-k materials include,without limitation, HfO₂, ZrO₂, Al₂O₃, TiO₂, Ta₂O₅, Sc₂O₃, lanthanideoxides and mixtures thereof, silicates and materials such as YSZ(yttria-stabilized zirconia), barium strontium titanate (BST), strontiumtitanate (ST), strontium bismuth tantalate (SBT) and bismuth tantalate(BT). Preferably, the high-k material is also deposited by an ALDprocess.

A layer or thin film 310 of a material such as TiN may be deposited overthe dielectric layer. Such a layer may act as an etch stop layer inwhich the etching has been previously performed in another reactor or inanother facility altogether. The transfer from one reactor or facilityto another can expose the thin films to contaminants such as water orair. The water or air generally oxidizes any exposed layer such as TiN,transforming the layer into essentially TiON. Such contamination caninterfere with the workfunction of the eventual stack.

A layer or thin film of TiAl or TaAl 320 is deposited over the layer 310by a deposition process as described herein, for example an ALD typeprocess, to form the illustrated structure. It will be appreciated thatin the illustrated embodiment the layers are not necessarily drawn toscale. The TiAl or TaAl layer, thin layer of TiN, and underlying high-kmaterial are patterned to form an electrode.

The TiAl or TaAl thin film 320 is preferably deposited over the thinfilm 310 by a deposition process as described herein above. In someembodiments the TiAl or TaAl thin film is deposited by an ALD typeprocess as described herein above. In some embodiments a TiAl or TaAlthin film is deposited by a cyclical deposition process comprising atleast one cycle comprising alternately and sequentially contacting thesubstrate with an Al precursor, such as TTBA and a Ti or Ta precursor,such as TiCl₄ or TaCl₅. In some embodiments at least one of the Ti or Taprecursor and/or Al precursor contacts the substrate in the presence ofa nitrogen precursor, such as N₂, although not necessarily in thisorder. In some embodiments the TiAl or TaAl thin film may comprisenitrogen. In some embodiments the Ti or precursor may comprise a halidecompound (e.g., TiCl₄ or TaCl₅) and the Al precursor may comprise anorganometallic compound, such as, e.g., tritertbutylaluminum (TTBA).

In some embodiments, the thin layer of TiN and/or the TiAl or TaAl layerare treated with a silane/borane agent after each or both layers havebeen deposited. The silane/borane agent can reduce the TiN and/or TiAlor TaAl layer. In some embodiments, where layer 310 may comprise TiON, asilane/borane agent may reduce the layer 310 to essentially TiN. Thus,in some embodiments where the layer 310 has been oxidized subsequent todeposition the work function of the reduced layer or layers may beimproved or restored to a value achieved prior to any oxidation of saidlayer or layers. In some embodiments the silane/borane agent may beselected from the group including silanes (e.g., SiH4, Si2H6, or Si3H8)and boranes (e.g., B2H6).

The thicknesses of the various layers in the stack may vary, though insome embodiments, such as the one illustrated in FIG. 3, layer 310 mayhave a thickness of about 10 Å to about 20 Å, preferably about 15 Å. Insome embodiments layer 320 may have a thickness generally greater thanthe thickness of layer 310. In some embodiments the use of a protectivetreatment, for example as described above with respect to the TiN andTiAl or TaAl layers, and in U.S. Pat. No. 8,841,182, incorporated hereinby reference, can have particular utility where the thicknesses of thevarious layers in a stack, such as the one illustrated in FIG. 3, arereduced to achieve smaller electronic devices and circuitry. This isbecause thinner layers are more prone to oxygen diffusing through them.And, in some embodiments, the use of a silane/borane agent does notappreciably increase the overall thickness of the stack.

When forming the TiAl or TaAl film, unreacted precursors and reactionbyproducts may be removed from the substrate surface after the substratethe substrate has been contacted with said precursor or precursors. Forexample, and as described herein above, unreacted precursor and reactionbyproducts, if any, may be removed from the substrate surface byevacuation and/or purging with an inert gas (e.g., N₂). In someembodiments, evacuation is achieved using a vacuum pump or a pluralityof vacuum pumps. In some embodiments wherein a TiAl or TaAl layer isdeposited by a cyclical deposition process as described herein above, adeposition cycle may be repeated until a TiAl or TaAl layer of thedesired thickness has been formed.

In some embodiments, a silane/borane agent is also or only applied afterall the deposition cycles of a desired deposition process have beencompleted. In some embodiments the silane/borane agent may be appliedeither as a pulse or a soak. In some embodiments, it may be preferableto apply the silane/borane agent as a soak after all the depositioncycles for the deposition of a given layer have been completed. Thus, insome embodiments a layer 310 may be deposited by a deposition processand a silane/borane agent may be applied to the layer 310 prior to thedeposition of a subsequent layer 320. In some embodiments a layer 310may be deposited by a deposition process and a layer 320 may then bedeposited by a deposition process as described herein above, for examplean ALD type deposition process. Subsequently the layer 320 may beexposed to a silane/borane agent. In some embodiments, the TiAl or TaAllayer has a thickness between about 5 Å and about 1000 Å after exposureto a silane/borane agent.

In some embodiments the TiAl or TaAl layer forms an electrode. In otherembodiments another conductive material, such as a metal or poly-Si, isdeposited over the TiAl or TaAl layer to thereby form an electrode. Theadditional conductive material may be deposited by ALD or by anotherdeposition process, such as by CVD or PVD. The deposition of asubsequent layer may be selective, or may be followed by patterningsteps. According to still other embodiments, annealing can be performedafter the deposition of a TiAl or TaAl layer. Suitable atmospheres forsuch annealing processes, such as N₂ or forming gas (N₂/H₂) are apparentto a skilled artisan.

In some embodiments further processing steps, such as spacer depositionand source/drain implantation, may be performed subsequent to thedeposition of the TiAl or TaAl layer as will be apparent to the skilledartisan.

The processes disclosed herein may be applied in a variety of contextswhere protecting a layer from oxidation or reducing the effect of oxygenon the properties of an oxidized layer may be beneficial. Althoughprimarily illustrated in the context of the fabrication of NMOStransistors, which may include planar “replacement gate” devices as wellas multiple gate transistors, such as FinFETs, the skilled artisan willbe aware of other relevant contexts in which the disclosed methods couldbe utilized, such as metal electrodes for memory structures where ann-type metal is needed.

Referring to FIG. 4, an exemplary embodiment of an NMOS stack 400 isillustrated. The stack 400 includes a dielectric layer 402, such ashafnium oxide, a first etch stop layer or bottom barrier layer 404, suchas a titanium nitride (TiN) layer, a first n-type metal layer, here theTiAl or TaAl layer 406, a second metal nitride layer 408, and a metallayer 410, such as a tungsten (W) layer. In some embodiments the TiAl orTaAl layer may comprise nitrogen. The presence of silicon 412 derivedfrom a protective treatment, as described in U.S. Pat. No. 8,846,550,incorporated herein by reference, is illustrated as being containedwithin the first metal nitride layer 404. While the silicon 412 may forma part of or be contained in any one of or more than one of theillustrated layers, FIG. 4 illustrates that the silicon 412 is locatedmore or less at the interface of the first metal nitride layer 404 andthe TiAl or TaAl layer 406.

In some embodiments, such as the one illustrated here, it may bebeneficial to provide a protective treatment as a part of the depositionof the etch stop layer 404 or prior to the deposition of the TiAl orTaAl layer 406, where the protective treatment may provide silicon 412(or boron), at least at or near the interface between the etch stop andn-metal films (the first metal nitride layer 404 and the TiAl or TaAllayer 406 as illustrated). In some embodiments, a protective treatmentis applied to the first etch stop layer 404 once the substrate has beenplaced in a chamber for depositing the TiAl or TaAl layer but beforedeposition of the TiAl or TaAl layer has begun. Of course, treatment maybe utilized to provide Si or B at the interface between any two layers.

In some embodiments the protective treatment may comprise exposing athin film comprising metal on a substrate to a treatment agentcomprising silane or borane. The treatment agent may react with oxygenthat may be present on or in the thin film or with oxygen uponsubsequent exposure of the thin film to oxygen or oxidizing agents. Insome cases, at least some oxygen is bound to metal atoms in the thinfilm, and with exposure to the treatment agent comprising silane orborane the metal oxygen bonds are reduced by preferential formation ofsilicon oxide or boron oxide. The silane or borane agent may also bindoxygen that is not bound to metal, such as oxygen that may be present inthe form of contaminants such as water, hydroxyl groups, etc.

As mentioned above, the treatment agent comprises one or more silanesand/or boranes, such as monosilane, disilane, trisilane, borane,diborane, and triborane.

The treatment agent may be applied in vapor or liquid form. However, thetreatment is typically carried out by providing a vapor phase pulse ofthe treatment agent. The length of time that the treatment agent isapplied may vary, for example depending on the thickness of the filmbeing treated and the amount of oxidation or the anticipated exposure tooxidizing agents. In some embodiments the treatment agent is contactedwith the film for a period of about 1 second to about 10 minutes, fromabout 2 second to about 5 minutes, from about 10 seconds to about 2minutes or from about 20 seconds to about 60 seconds. However, shorteror longer exposures can be utilized. For example, in some embodimentsthe treatment agent may be applied as a relatively short pulse, such asless than about 1 second. In some embodiments a partially or completelydeposited film is soaked in the treatment agent, such as for 1 second ormore, 10 seconds or more, 20 seconds or more, 30 seconds or more, or 60seconds or more. In some embodiments the soak may be for at least oneminute, two minutes, five minutes, ten minutes or more. Specifictreatment times can be determined by the skilled artisan depending onthe particular circumstances such as the type of film, thickness of thefilm, amount of existing oxidation of the film and the type of exposureto oxidizing agents that is anticipated.

In some embodiments, a thin film of the present disclosure is depositedaccording to a known process, such an ALD or a CVD process. A protectivetreatment can then be applied to the thin film after the thin film hasbeen fully deposited. However, in some embodiments, the protectivetreatment forms a part of the deposition process. For example, where anALD type process is used, such as in the deposition of a TiAl or TaAllayer, the protective treatment may comprise one step of at least onedeposition cycle. In some cases, the protective treatment is provided ina certain number of ALD cycles or all of the ALD cycles. For example,the protective treatment may be provided as a separate pulse in everyALD cycle, or provided every 2, 3, 4, 5, 10, 20 or more ALD cycles. ForCVD deposition, the CVD deposition process may be interrupted one ormore times during deposition to provide the treatment agent. In someembodiments, the protective treatment is applied as the last pulse orexposure in the deposition process.

The use of a protective treatment can bind up at least some of theoxygen that may be present initially, or upon subsequent exposure, suchas during transport from one chamber to another. The use of a protectivetreatment may also reduce at least some of the previously oxidizedportions of a thin film, such as the first metal nitride layer 404. Forexample, substrates may be received that already contain an etch stoplayer (or bottom barrier layer), such as a TiN layer, and that layer canbe treated as described herein by exposure to a treatment agent prior tosubsequent processing.

The thicknesses of the various layers in the stack 400 may vary, thoughin some embodiments, such as the one illustrated in FIG. 4, the firstmetal nitride layer 404 may be from about 5 Å to about 20 Å thick, forexample about 15 Å thick, and the second metal nitride layer may beabout 30 Å to about 50 Å thick. The use of a protective treatment aspresently disclosed can have particular utility where the thicknesses ofthe various layers in a stack, such as stack 400, are reduced to achievesmaller electronic devices and circuitry.

The protective treatments disclosed herein could be applied to any oneor more of the layers 402, 404, 406, 408, or 410 before, during, orafter the deposition of each thin film. In some embodiments, it ispreferable to treat one or both of layers 404 and 406. In someembodiments, it may be preferable to treat one or more of layers 404,406, and 408. The use of a protective treatment before or during theformation of the NMOS workfunction setting layer (the TiAl or TaAl layer406 as illustrated) has been mentioned; however a treatment agent couldalso or alternatively be applied before or during the deposition of thefirst etch stop layer (the first metal nitride layer 404). In someembodiments, the use of a protective treatment on the first metalnitride layer 404 may eliminate or reduce the need for such a treatmentof any subsequent layers or at least the NMOS workfunction setting layer406. Similarly, the use of a protective treatment before, during, orafter the formation of the TiAl or TaAl layer 406 may eliminate orreduce the need for a similar treatment to subsequent layers,particularly if a treatment applied to the TiAl or TaAl layer 406preserves the work function of the overall stack 400 irrespective ofmoderate oxidation of the subsequent layers 408 or 410.

However, in some embodiments, it may be beneficial to treat the secondmetal nitride layer 408 and/or the metal layer 410. As with the lowerlayers, a protective treatment may reduce oxidized portions of thoselayers, scavenge oxygen contaminates, and/or prevent subsequentoxidation when exposed to contaminates or the atmosphere.

Irrespective of the layer being discussed, the same methods for applyingthe protective treatment can be used. In some embodiments the treatmentagent is provided as a pulse as a part of a deposition cycle. In someembodiments a deposited film, or portion of a deposited film is soakedin the treatment agent. For example, a protective treatment could beincorporated into the process for forming the TiAl or TaAl layer 406.And the treatment agent could be provided in every deposition cycle orjust in some cycles.

With reference again to FIG. 4, in some embodiments a first metalnitride layer 404 is deposited over the dielectric layer 402, which maycomprise a dielectric material such as hafnium oxide. A protectivetreatment may be applied before, during, and/or after the deposition ofthe first metal nitride layer 404. In some embodiments, it is desirableto apply a protective treatment to a completed first etch stop layer,such as a TiN layer, prior to the deposition of the NMOS workfunctionsetting layer, such as TiAl or TaAl layer 406, even if a protectivetreatment was used in the deposition of the first etch stop layer. Forexample, if some time has passed from the time the first metal nitridelayer 404 was deposited and the time when the TiAl or TaAl layer 406 isdeposited. Such a delay may increase the chances that the first metalnitride layer will be exposed to water, air, etc. Again, whileillustrated in the context of forming TiAl or TaAl films in the contextof an electrode and an NMOS stack, other contexts will be apparent tothe skilled artisan.

Again referring to FIG. 4, the TiAl or TaAl layer 406 can be depositedover the first metal nitride layer 404. A protective treatment may beapplied before, during, and/or after the deposition of the TiAl or TaAllayer 406. FIG. 5A illustrates one possible process where a titaniumnitride layer is provided at step 502, and a TiAl or TaAl layer, isdeposited over the titanium nitride layer at step 504. A protectivetreatment is then applied to the deposited TiAl or TaAl layer at step506. In some embodiments, application of a protective treatment duringor before the deposition of the work function setting TiAl or TaAl layer406 may help minimize the presence of oxygen in the film while the TiAlor TaAl layer 406 awaits the second metal nitride layer 408 in aclustered or declustered process. The protective treatment applied atstep 506 may comprise soaking the deposited TiAl or TaAl layer in atreatment agent comprising silane or borane. The protective treatmentmay reduce or bind to oxygen contaminates in the TiAl or TaAl layer n.

FIG. 5B illustrates one process where a titanium nitride layer isprovided at step 512, and a protective treatment is applied to thetitanium nitride layer at step 514. A TiAl or TaAl layer is thendeposited according to a deposition process as described herein above atstep 516. In this process, free oxygen that may have been present in oron the titanium nitride layer may be bound up by the protectivetreatment agent so as to prevent or reduce oxidation of the TiAl or TaAldeposited in step 516.

Other materials may also benefit from the application of a protectivetreatment according to the present disclosure. All NMOS workfunctionlayers, such as pure metals like Al and Ti, or transition metalnitrides, carbides, borides, silicides, etc. may suffer from oxygenincorporation making them more p-type. Accordingly, a protectivetreatment could be applied to films comprising any of such materials.

FIG. 5C illustrates one process where a titanium nitride is provided atstep 522, and a TiAl or TaAl layer is deposited by a deposition processas described herein above at step 524 in which a protective treatment isincorporated into one or more of the deposition cycles. For example, theprotective treatment may comprise a step in only one cycle or maycomprise a step in a certain number of cycles, such as every other cycleor every third, fourth, fifth, sixth, seventh cycle, etc.

In some embodiments, the deposition of the TiAl or TaAl layer at step524 may comprise a deposition process comprising at least one depositioncycle comprising:

contacting the substrate with a first vapor phase precursor comprisingTi or Ta, for example TiCl₄ or TaCl₅;

removing excess first precursor and reaction by products, if any, fromthe substrate;

contacting the substrate with a second vapor phase precursor comprisingAl, for example TTBA;

removing from the substrate excess second precursor and any gaseousby-products;

wherein at least one of the contacting the substrate with a first vaporphase precursor comprising Ti or Ta and contacting the substrate with asecond vapor phase precursor comprising Al steps occurs in the presenceof a nitrogen precursor;

optionally contacting the substrate with a protective treatment agentcomprising a silane or borane; and

optionally repeating at least the first vapor phase precursor and secondvapor phase precursor contacting and removing steps until TiAl or TaAlthin film n of the desired thickness has been formed.

In some embodiments, the deposition of the TiAl or TaAl layer comprisingnitrogen at step 524 may comprise a deposition process comprising atleast one deposition cycle comprising:

exposing the substrate to a first vapor phase precursor comprising Ti orTa, for example TiCl₄ or TaCl₅;

exposing the substrate to purge gas and/or removing excess firstprecursor and reaction by products, if any, from the substrate;

exposing the substrate to a second vapor phase precursor comprising Al,for example TTBA;

exposing the substrate to purge gas and/or removing from the substrateexcess second precursor and any gaseous by-products;

wherein at least one of the exposing the substrate to a first vaporphase precursor comprising Ti or Ta and exposing the substrate to asecond vapor phase precursor comprising Al steps occurs in the presenceof a nitrogen precursor;

optionally exposing the substrate to a protective treatment agentcomprising a silane or borane; and

optionally repeating at least the first vapor phase precursor and secondvapor phase precursor exposing and removing steps until TiAl or TaAlthin film comprising nitrogen of the desired thickness has been formed.

In some embodiments the contacting the substrate with a protectivetreatment agent step can be included in each deposition cycle or only insome of the deposition cycles. Thus in some embodiments the first vaporphase precursor and second vapor phase precursor contacting and removingsteps can be repeated several times before the contacting the substratewith a protective treatment agent step is introduced. The contacting thesubstrate with a protective treatment agent step may also be used priorto any deposition cycle or only as the first step in the firstdeposition cycle. Application of a protective treatment prior to anydeposition cycle for depositing the TiAl or TaAl layer 406 may bedesirable where the first metal nitride layer 404 has already beenoxidized, such as where the first metal nitride layer has served as anetch-stop layer in a prior process. In such cases, it may be desirableto apply the protective treatment as a soak of a treatment agentcomprising silane or borane prior to depositing the TiAl or TaAl layer406. In some embodiments where the TiN layer 404 is treated, protectivetreatment during or after the deposition of the TiAl or TaAl layer 406is not utilized. However, in some embodiments where the first metalnitride layer 404 has been treated, it may still be desirable to apply aprotective treatment during or after the deposition of the TiAl or TaAllayer 406.

In some embodiments, NMOS stacks containing TiAl or TaAl layersfabricated using the methods disclosed herein exhibit a leakage (J_(g))(at −1V stress) of less than about 10⁻² A/cm², less than about 10⁻³A/cm², or less than about 3*10⁻⁴ A/cm².

In some embodiments of the present disclosure, TiAl or TaAl layers canbe formed in NMOS stack application in which the equivalent oxidethickness, or EOT, of the thin films can be less than about 1.3 nm, lessthan about 1.2 nm, preferably less than about 1.1 nm, less than about1.05 nm or less than about 1.0 nm. In some embodiments the thickness ofTiAl or TaAl films in NMOS stack application is from about 10 Å to about100 Å, from about 15 Å to about 75 Å, from about 20 Å to about 50 Å. Insome embodiments the thickness of TiAl or TaAl films is less than about50 Å or less than about 30 Å. In other embodiments the thickness of TiAlor TaAl films is from about 5 Å to about 1000 Å, from about 15 Å toabout 500 Å, or from about 20 Å to about 200 Å. In some embodiments thethickness of TiAl or TaAl films is less than about 500 Å or less thanabout 100 Å thick.

In some embodiments of the present disclosure, TiAl or TaAl layerscomprising nitrogen can be formed in which the effective workfunction,or eWF, can be from about 4.0 to about 4.9 eV, from about 4.1 to about4.6 eV, or from about 4.15 to about 4.3 eV. In some embodiments TiAl orTaAl layers comprising nitrogen can be formed in which the effectiveworkfunction, or eWF, can be less than about 4.5 eV, less than about 4.4eV, less than about 4.3 eV or less than about 4.25 eV. In someembodiments the work function of a TiAl or TaAl material is measuredusing TiAl or TaAl films from about 10 Å thick to about 100 Å thick,from about 15 Å thick to about 75 Å thick, or from about 20 Å thick toabout 50 Å thick. In some embodiments the work function of a TiAl orTaAl material is measured using TiAl or TaAl films less than about 50 Åthick or less than about 30 Å thick.

In some embodiments, the use of a protective treatment such as a silane(e.g., disilane or trisilane) can reduce the resistivity of a TiAl orTaAl layer relative to a TiAl or TaAl layer to which a protectivetreatment is not exposed. In some embodiments, the resistivity isreduced up to or as much as about 30%, up to or as much as about 40%, orup to or as much as about 50%. In some embodiments, such as where aprotective treatment is applied as soak after deposition, resistivityreduction may be as much as about 5%, as much as about 10%, or as muchas about 20%.

Again referring to FIG. 4, a metal layer 410 may be deposited by anyknown method. A protective treatment may be applied before, during,and/or after deposition of the metal layer 410. In some embodiments, asecond metal nitride layer 408 is provided, and the metal layer 410 isdeposited over the metal nitride layer 408. The second metal nitridelayer 408 can be deposited over the TiAl or TaAl layer 406. A protectivetreatment may be applied before, during, and/or after the deposition ofthe second metal nitride layer 408, similar to the first metal nitridelayer 412. In this process, free oxygen that may have been present in oron the second metal nitride layer 408 may be bound up by the protectivetreatment so as to not oxidize the subsequently deposited material.Reducing the amount of free oxygen in the second metal nitride layer 408may have the added benefit of diminishing the amount of oxygen thatcould diffuse down into the stack 400 during subsequent processes, suchas downstream thermal processing, diffusion that could actually reachthe workfunction layer (i.e., the TiAl or TaAl layer 406).

A protective treatment may be applied to the completed metal layer 410.The protective treatment may be applied as a soak to the deposited metalfilm. In some embodiments, a metal layer is deposited by an ALD methodin which a protective treatment is incorporated into one or more of thedeposition cycles. For example, the protective treatment may comprise astep in only one deposition cycle or may comprise a step in a certainnumber of cycles, such as every fifth, tenth, twentieth cycle, etc.

Again, while illustrated in the context of treating thin films in anNMOS stack, other metal-containing films can be treated as well. Theexact composition of metal thin films produced and/or treated using themethods and materials disclosed herein may vary. For example, TiAl orTaAl films fabricated according to the present disclosure may contain anumber of differing elemental components including, but not limited totitanium, aluminum, carbon, silicon and/or boron depending in part onthe type of protective treatment used.

In some embodiments, the atomic percentage of silane or borane presentin a film after treatment could be greater than about 10%, greater thanabout 25%, or greater than about 35%. In embodiments where theprotective treatment is applied as soak, the silane or borane may bevery concentrated at those surfaces that were treated, with theconcentration dropping off rapidly below those surfaces. In embodimentswhere the protective treatment is applied as a part of a depositionprocess, such as in an ALD type process, the silane or boraneconcentration may be from about 5% to about 50%.

In at least some of the aforesaid embodiments, any element used in anembodiment can interchangeably be used in another embodiment unless sucha replacement is not feasible.

It will be appreciated by those skilled in the art that various otheromissions, additions and modifications may be made to the methods andstructures described above without departing from the scope of theinvention. All such modifications and changes are intended to fallwithin the scope of the invention, as defined by the appended claims.

What is claimed is:
 1. A process for depositing a metal aluminum thinfilm comprising nitrogen and having a work function of less than 4.5 eVon a substrate in a reaction space, the process comprising at least onedeposition cycle comprising alternately and sequentially contacting thesubstrate with a vapor phase metal precursor and a vapor phase aluminumprecursor comprising tritertbutylaluminum (TTBA), wherein the vaporphase aluminum precursor contacts the substrate in the presence of avapor phase nitrogen precursor comprising N₂ so that the N₂ reacts withthe aluminum precursor while the vapor phase aluminum precursor contactsthe substrate, wherein the metal aluminum thin film comprises at least5% nitrogen on an atomic basis, and wherein the at least one depositioncycle is carried out at a temperature from 250° C. to 500° C.
 2. Theprocess of claim 1, wherein the vapor phase nitrogen precursor isintroduced into the reaction space concurrently with the vapor phasemetal precursor.
 3. The process of claim 1, wherein the metal istitanium or tantalum.
 4. The process of claim 1, wherein the metalaluminum thin film comprises up to 25% nitrogen on an atomic basis. 5.The process of claim 1, wherein the metal aluminum thin film comprisesup to 60% carbon on an atomic basis.
 6. The process of claim 1, whereinthe vapor phase metal precursor is TiCl₄ or TaCl₅.
 7. The process ofclaim 1, wherein the at least one deposition cycle is carried out at atemperature from 300° C. to 400° C.
 8. The process of claim 1, whereinthe vapor phase nitrogen precursor serves as a carrier gas for one orboth of the vapor phase metal precursor and the vapor phase aluminumprecursor.
 9. The process of claim 1, wherein all of the nitrogen in themetal aluminum thin film comes from the vapor phase nitrogen precursor.10. The process of claim 1, further comprising contacting the substratewith a protective treatment reagent comprising silane or borane in eachdeposition cycle.
 11. The process of claim 10, wherein the silane orborane is selected from the group consisting of monosilane, disilane,trisilane, borane, diborane, and triborane.
 12. The process of claim 1,wherein the process is an atomic layer deposition process.
 13. Theprocess of claim 1, wherein the vapor phase nitrogen precursor flowscontinuously into the reaction space throughout the deposition cycle.14. A process for depositing a metal aluminum thin film on a substratein a reaction space, the process comprising multiple deposition cyclescomprising: contacting the substrate with a first vapor phase metalprecursor; removing excess first vapor phase metal precursor andreaction byproducts, if any, from the substrate; contacting thesubstrate with a second vapor phase aluminum precursor comprisingtritertbutylaluminum (TTBA); and removing excess second vapor phasealuminum precursor and reaction byproducts, if any, from the substrate;wherein the metal aluminum thin film comprises at least 5% nitrogen onan atomic basis and has a work function of less than 4.5 eV, wherein thesubstrate is contacted with a vapor phase nitrogen precursor comprisingN₂ concurrently with the second vapor phase aluminum precursor or bothof the first vapor phase metal precursor and the second vapor phasealuminum precursor so that the N₂ reacts with the aluminum precursorwhile vapor phase aluminum precursor contacts the substrate, and whereinthe multiple deposition cycles are carried out at a temperature of 250°C. to 500° C.
 15. The process of claim 14, wherein the multipledeposition cycles are carried out at a temperature of 300° C. to 400° C.16. The process of claim 14, wherein the metal in the first vapor phasemetal precursor is titanium or tantalum.
 17. The process of claim 14,wherein the first vapor phase metal precursor comprises TiCl₄ or TaCl₅.18. The process of claim 14, wherein the substrate is only contactedwith a protective treatment reagent comprising silane or borane afterevery 2, 5, 10, 20 or more deposition cycles.
 19. The process of claim14, wherein the vapor phase nitrogen precursor further comprises NH3,hydrazine, hydrazine derivatives, or molecular nitrogen.
 20. The processof claim 14, wherein all of the nitrogen in the metal aluminum thin filmcomes from the vapor phase nitrogen precursor.